Directive antenna system



Sept. 23, 1952 A. s. CLAVIER Filed Jan. 16, 1947 DIRECTIVE ANTENNA SYSTEM 2 SHEETS-SHEET 1 II III! "hi Mum min IIYVENTOR. AND/Pf G. CZ/lV/f/P ATTORNEY A. G. CLAVIER DIRECTIVE ANTENNA SYSTEM Sept. 23, 1952 2 sHEETssHEET 2 Filed Jan. 16, 1947 {NVENTOR HNDRE A TYUFNEY Patented Sept. 23, 1952 UNITED STATES DIRECTIVE ANTENNA SYSTEM corporation of Delaware PATENT OFFICE Application January 16, 1947, Serial No. 722,440

Claims.

This invention relates to directive radio transmitters, and particularly to rotating directive radio transmitters provided with a, lens system for producing a desired directivity pattern.

Various directive transmitters, such as radio beacon systems are in use today providing a lens system for controlling the phase velocity of electromagnetic waves for producing desired directivity patterns. Where a high speed rotating ultra high frequency beam is desired, it has been necessary that the radiator and lens system be rotated for .scanning purposes. The present invention employs a fixed outer lens structure within which a rotary movable central radiating system is mounted whereby higher angular speeds are possible.

It is one object of this invention to provide means for obtaining higher angular speeds of ultra high frequency directional radio beam displacement.

It is another object of this invention to provide means for obtaining high rotary speeds of ultra high frequency beams, using a lens system for varying the phase velocity of radiated waves to produce a desired directivity pattern.

It is another object of this invention to provide a relatively fixed phase velocity lens system associated with a rotatable radio beacon for determining the phase of the radiated energy at desired points in space, and/or a rotatable lens portion movable with the antenna to provide concentration in another angle.

Briefly, use is made of the difference of phase velocity of electromagnetic waves propagated in free space and bounded space.

According to one feature of my invention, a rotatable source of ultra high frequency radiant energy is provided having a predetermined relatively fixed lens structure surrounding the source of rotating energy, the formation of the lens structure controlling the phase of the propagated wave-fronts, and accordingly the beam shape of the energy in one planar coordinate.

According to another feature of my invention, the central rotating radiator is provided, with a predetermined lens structure for providing additional control of the phase of the propagated wave-fronts in another coordinate to define a pencil beam.

While my invention itself is defined in the appended claims, the invention, together with other and further objects and features thereof, will be best understood from the following description of an embodiment thereof, reference being made to the drawing in which:

Figure 1 illustrates in perspective an electromagnetic horn for directing radiant energy through a phase velocity lens system, according to my invention;

Figure 2 is a sketch used in describing phase velocity control of electromagnetic waves in the vertical plane;

Figure 3 is a sketch used in describing compensating phase velocity control of electromagnetic waves for producing a desired directivity pattern of radiated energy.

Figure 1 is a radio beam system comprising a source of radiant energy I and means 2 for directing the radiant energy through a phase velocity lens system 3. A motor 4 is provided for rotating the source of radiant energy and the directing means to produce a, rotating beam. Normally, radiant energy leaving source I and directed by the radiator 2 into space has a phase curvature of the wave-front, due to the divergence of the waves. According to this invention, there is provided a lens 3 which consists of a plurality of metallic plane surfaces, properly shaped, so that if the beam energy passes therebetween, divergence and consequent curvature may be corrected for in a given plane. For example, with vertically polarized energy, the planes will extend vertically and produce an equiphase or parallel wave-front in the vertical plane.

For use in a rotatable beam system, the vertical correcting apparatus may comprise a plurality of plates 5, Figure 1, arranged in a circle having an axial diameter sufliciently large compared with the wave-length of the radiant energy frequency in air so that two adjacent metallic plates may be considered as substantially parallel at the points where the beams passes therebetween. The spacing between the plates determines the phase velocity of the waves transmitted therebetween for the particular operating frequency. Retaining rings 6 may be used to maintain the plates in place.

In order that energy at the outer surface CB, Figure 2, of the cylindrical arrangement of plates be all in the same phase, it is necessary that energy travelling along the path AC arrive at the outer surface of the cylinder at the same time as energy travelling along the path AB. If 0 be designated as the time taken for the wave to travel from A to B, then we should have tween the metallic plates and V is the phase velocity of the wave at the central part of the beam. Hence, by varying the width of the vertical plates for difierent angles of radiation from source A, the time of arrival of the radiant energy can be determined to occur at the same time along the outer surface of the cylinder.

The use of such plates will provide for equiphase of signals on the external surface of the cylindrical structure, but this would not produce the required directivity for a directive beam. In order to achieve this, equiphase must be obtained on a suitable portion of the tangent plane to the outer cylinder. This can be obtained by means of a compensating device 2, Figure l, which is added to the central radiating system and rotates with it. To determine the shape of these additional metallic plates, let us consider the Figure 3. This is a horizontal cross-section of the system. If BC designates the outer surface of the cylindrical structure of metallic plates, and BD the plane tangent to the cylinder, it is necessary, in order to achieve the desired directivity, that the time taken for the wave to travel through paths AB and AD must be the same. If is designated as the time it takes the wave to travel from A to B in the absence of the compensating plates, the time taken with them will be where P0 is the distance covered inside the compensating plates in direction AB. For any angle, the corresponding distance inside the compensating system should be P such that Figure 1 shows a perspective View of a compensating structure designed according to the above formula. The vertical flanges of this horn and inside compensating plate should be cut on an angle corresponding to the height of the vertical metallic plates.

This height, as well as the horizontal width of the rotating horn, is determined by the sharpness of the beam which it is intended to produce. The area A of the fictitious equiphase tangent plane which acts as a sending electromagnetic radiator is substantially related to the gain in the direction of the axis of the beam by the following equation:

where G is the gain in power compared with the power received in the equatorial plane of a halfwave antenna, K is a numerical factor which is the order of 4, and A is the wavelength at the system operating frequency.

On the other hand, the width of the beam in degrees B between half-power points, and the gain are related substantially in such cases by a semi-empirical law such as:

B2GE25,0O0

If an equiphase plane of area A=D is considered, the following approximate relationship is obtained.

Thus, for a 5,000 megacycle per second wave and a beam width of 5 degrees, D, according to the formula, would be equal to 96 cm.

The construction of the central horn may require careful attention as to the design of the rotating point, and the whole structure corrected experimentally to achieve the nicety of results required. The shape of the outer surrounding section, acting as a phase velocity lens may be of almost any volumnar configuration. For example, in case the beam is required to be sent upwards instead of horizontally, a similar arrangement, but conical instead of cylindrical can be used.

The idea of the central compensating device may .be extended to other types of fixed internal structures, derived for instance, from a horn or parabolic shape by rotation around the vertical axis of the ystem.

A number of slightly slanting horizontal plates, separated by the same distance as the vertical plates, can be used to make the arrangement sensitive to horizontally polarized electromagnetic waves. Applicants rotatable beam system lends itself to a variety of configurations. The vertical correcting apparatus may comprise a plurality of plates arranged in spaced relation from the central radiator and from each other and having substantially any configuration, the space relations being such that the blades are substantially parallel at the points where the beam passes therebetween. The radiators may be then provided with a horizontal compensating arrangement.

Since the radiating cone itself is of relatively small dimension and may be easily rotated, also, since correction for curvature of the wave is provided in both the vertical and horizontal, a substantially parallel beam of sharpness dependent upon the correcting effect is provided.

While I have described above the principles of my invention in connection with specific apparatus, it is to .be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention.

I claim:

1. A directive radio system comprising a central source of radiant energy, said central energy source comprising a rotating horn for forming said radiant energy into a beam, a fixed lens system surrounding said rotating horn for controlling the .phase velocity of the radiated electromagnetic waves, said lens system comprising a plurality of plane, metallic plates arranged in a circle of an axial diameter sufiiciently large compared with the wavelength of the radiant energy so that two adjacent metallic plates may be considered as having substantially parallel surfaces where the beam passes therebetween, each of said surfaces being aligned substantially parallel to the respective directions of radiant energy propagation thereby for providing an equl-phase of the radiant energy outside of said surrounding lens system after passage of the radiant energy between said plates.

2. A directive radio system comprising a source of radiant energy, means for rotatably directing the energy of said source comprising a rotatable horn in the form of a first lens system coupled to said source for controlling the phase velocity of the radiated electromagnetic waves, a second relatively fixed lens system extending about said source and said horn over a predetermined angular position of are for controlling the phase velocity of the radiated electromagnetic waves, said first and second lens systems respectively comprising first and second spaced, plane, me-

tallic surfaces respectively arranged around a circle concentric with said source, each of said first and second metallic surfaces extending radially with respect to said source, whereby the energy from said source is passed between adjacent surfaces of said first and second lens systems, respectively, for producing a desired directively pattern of the radiant energy, said lens systems comprising predetermined lengths of said first and second surfaces in the direction of the radii of said are.

3. A directive radio system comprising a source of radiant energy, said source comprising a rotatable horn in the form of a lens system for controlling the phase velocity of the radiated electromagnetic waves, a second relatively fixed lens system surrounding said source for controlling the phase velocity of the radiated electromagnetic waves, said second lens system comprising substantially plane, metallic plates arranged around a circle concentric with said source. the surfaces of said plates extending along diiferent radii of said circle and having different predetermined widths along the length perpendicular to said radii, said first lens system comprising metallic plates extending along different radii of said circle, said first and second lens system producing a desired directivity pattern of the radiant energy.

4. A directive radio system comprising a source of radiant energy, said energy source comprising a rotatable born for forming the radiant energy into a beam, a fixed lens system surrounding said rotatable horn for controlling the phase velocity of the radiated electromagnetic waves, said lens system comprising a plurality of substantially plane, metallic plates arranged in a circle concentric with said horn and having an axial diameter sufficiently large compared with the wavelength of the radiant energy so that adjacent metallic plates may be considered as substantially parallel where the beam passes therebetween, each of said plates being aligned substantially parallel to its respective direction of radiant energy propagation and having predetermined lengths in the direction of radiant energy propagation thereby for providing an equiphase of the radiant energy outside of said surrounding lens system after passage of the radiant energy between said plates.

5. A directive radio system comprising a sourceof radiant energy, said energy source comprising a rotatable horn for forming said radiant energy into a beam, a fixed lens system extending about said horn and said source over a predetermined angular portion of are for controlling the phase velocity of the radiated electromagnetic waves, means for rotatably directing the energy of said source toward said lens system for passage therethrough comprising said horn coupled to said source, said fixed lens system comprising a plurality of spaced, substantially plane, metallic surfaces arranged in a circle concentric with said source and having an axial diameter sufliciently large compared with the wavelength of the radiant energy so that two adjacent metallic surfaces may be considered as substantially parallel where the beam passes therebetween, each of said surfaces being aligned substantially parallel to its respective direction of radiant energy propagation and having different predetermined widths in the direction perpendicular to the plane of said circle for providing an equi-phase of the radiant energy outside of said surrounding lens system.

ANDRE G. CLAVIER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,904,901 Lawrence Apr. 18, 1933 2,075,808 Fliess Apr. 6, 1937 2,223,224 Newhouse Nov. 26, 1940 2,231,929 Lyman Feb. 18, 1941 2,288,177 Bailey June 30, 1942 2,354,665 Church et al Aug. 1, 1944 2,442,951 Imas June 8, 1948 2,460,401 Southworth Feb. 1, 1949 OTHER REFERENCES Radio News, May 1946, pages 3, 5 and 29. Proc. I. R. 22., vol. 34; pages 828 to 836, November 1946. 

